1. Field of the Invention
The invention relates a light guide plate and a backlight module having improved luminance uniformity.
2. Description of the Related Art
Typically, a linear light source such as a cold-cathode fluorescent lamp (CCFL) is often used in a backlight module; however, it is bulky and thus not suitable for a compact electronic product such as a handheld display. In contrast, a point light source such as a light-emitting diode (LED) is fit for such kind of electronic product due to its small size.
FIG. 1 shows a schematic diagram illustrating a conventional backlight module using a point light source. Referring to FIG. 1, point light sources 104 such as light emitting diodes are positioned next to one side surface 102a of a light guide plate 10, and the top surface 102b and the bottom surface 102c of the light guide plate 10 which are opposite to each other are both provided with prismatic structures formed by V-shaped grooves 106.
As to a point light source, the relationship between the radiant power and the angle between the observer's line of sight and the surface normal is governed by the Lambert's emission law. Hence, in case a point light source 104 is used as a side light source of a backlight module and the propagation direction of its emitting light is directed toward the normal of the light-emitting surface 102b with the aid of a prism sheet (not shown), multiple bright stripes 110 having comparatively high brightness often emerge on the light guide plate 10 at locations near the side surface 102a to cause inferior luminance uniformity, as shown in FIG. 2.